The present invention relates to an apparatus for the detection of splits in logs and other wooden members, and specifically to an apparatus employing ultrasonic energy to detect and characterize such splits. The wooden members may be trees, logs, beams, planks, lumber, boards or wood composites and the like.
When logs are sawn to size in the field using commercial harvesters, they are often subject to the creation of splits when cut. This is because one end of the log is unsupported during the cutting operation. Splits also occur when the tree is initially felled. The splits are undesirable, introduce defects in the lumber that is sawn from the logs, and thereby reduce the value of the log itself. A recent examination of the problem indicates that up to 70% of logs harvested in this manner contain splits. If the problem is detected in the field at the time of sawing, then either the operator can modify his/her practice to reduce this incidence, or the logs can be cut longer such that sufficient material will remain free of defects. In other words, if a 12 foot long clear log is desired, and the harvester detects end splits for a distance of 12 inches, then the next cut will be made so as to have the required 12 feet after the defective portion is removed. Traditionally identification of defects and other features affecting lumber grade has been performed visually, for example, by a saw operator visually inspecting the log or board prior to determining the necessary cross or rip cuts that will yield the best product output or yield. Recently a number of electronic scanning systems have been produced using cameras and lasers to automate this visual process. Such optical techniques are limited to the detection of superficial defects in the wooden members and even these techniques may be defeated by dirt, bark, stain or other markings on the outside of the log. More importantly, internal defects such as splits are generally not visible.
What is needed is an apparatus for detecting and characterizing splits internal to a wooden member, that is also robust against the harsh environment of a typical lumber operation or the like and that is safer, less costly and more compact than instruments based on x-rays or other electromagnetic radiation.